Shadow compression

Software RawTherapee
1

Hi,
I am new to RT and I am trying to get the more “neutral” set up. Please, can someone explain:

  1. what is the “black level” slider exactly (mathematically) doing?
  2. what is the “shadow compression” slider exactly (mathematically) doing? To avoid any “tricks” should I set it to 50% or to 0 ?

I have read the manual but it is not very clear to me how these sliders (mathematically) work

Thanks so much!!

Manuel